Various types of dead bolts, well known in the prior art, are used to selectively prevent opening of a door. Such dead bolts are generally affixed to a door jamb and have a slidable rod which engages the door when it is closed to prevent its opening. Alternatively, the rod may be affixed to the door and engage the door jamb to prevent opening of the door.
Portable door locks similar to dead bolts are also well known in the art, such as disclosed in U.S. Pat. Nos. 1,947,773, 3,913,962, and Re. 28,893. Portable door locks are for use in combination with a door frame assembly supporting a door and having a door jamb with a latch recess for engaging a latch on an edge of the door. For example, such portable door locks include a plate having a plurality of square apertures within which a bolt may be located. A lug on the plate is located in the latch recess and the door is closed so that the plate is located between the door jamb and the door and protrudes therefrom. The bolt is then located within one of the square apertures to preclude the door from opening (see U.S. Pat. No. 2,804,332 issued to Franklin). However, the portable door locks of the prior art, in general, are expensive to manufacture, are not adapted to accommodate various standard door thicknesses and employ bolts which do not firmly and conveniently engage the plate.